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February 24, 2013

Evolution Gave Humans Unique Brain Structures Over Primates

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redOrbit Staff & Wire Reports - Your Universe Online

Researchers have discovered a pair of functional networks in the human cerebral cortex that are not present in the brains of rhesus macaque monkeys, leading them to theorize that the networks were added during the evolution from ancient primates to the modern day homo sapiens.

The networks were discovered by a team of researchers led by neurophysiologist Wim Vanduffel of University of Leuven and Harvard Medical School (HMS), who analyzed fMRI (functional Magnetic Resonance Imaging) scans of both humans and rhesus monkeys as they participated in different activities, said Selena Hill of Latinos Post.

As a result of their discovery, Vanduffel and his Italian and American colleagues believe that there must have been an evolutionary divergence between the ancestors of mankind and those of the rhesus monkeys that took place approximately 25 million years ago.

At that time, they said, some areas of the brain were either added, removed, or functionally altered, leading to speculation that they may have uncovered evidence to support the theory that the evolutionary process helped give modern humans unique cerebral structures.

"We did functional brain scans in humans and rhesus monkeys at rest and while watching a movie to compare both the place and the function of cortical brain networks,” Vanduffel said Friday in a statement. "Even at rest, the brain is very active. Different brain areas that are active simultaneously during rest form so-called 'resting state' networks.”

“For the most part, these resting state networks in humans and monkeys are surprisingly similar, but we found two networks unique to humans and one unique network in the monkey,” he added. “When watching a movie, the cortex processes an enormous amount of visual and auditory information. The human-specific resting state networks react to this stimulation in a totally different way than any part of the monkey brain. This means that they also have a different function than any of the resting state networks found in the monkey.”

Essentially, the professor explained, not only are there specific brain structures that are found in humans but absent in the brains of the monkeys, but there are no similar structures capable of performing the same types of functions. Those unique brain regions are located high in the back and at the front of the cortex, and are most likely associated with human intelligence and other types of cognitive abilities unique to our species.

Last summer, a team led by Vanduffel demonstrated for the first time that they could alter the behavior of monkeys by using optogenetics — a state-of-the-art neuromodulation technique that uses light to control brain cells.

He and his colleagues used pulses of blue light to affect the neurons responsible for a specific set of eye movements — a discovery that they believe could ultimately be adapted to work in humans for therapeutic needs and care. Their findings were published in the journal Current Biology.